The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
Forced commutated converters have now become an attractive choice in high voltage, high power transmission and distribution applications due to the rapid development in power semiconductor technologies and other additional advantages like full real-reactive power control, dynamic voltage regulation, black start capability, etc. This technology initially started with the voltage source converters (VSC) has now led to many new multilevel topologies with advanced features. A well-known topology is the Modular multilevel converter (MMC). Due to the modular structure, the topology is compact and scalable to reach any number of voltage levels by simple series connection of submodules resulting in higher reliability and easy maintenance.
Over the years, researchers have studied different MMC topologies in attempts to improve its features. However, most of the converter topologies still focused on the conventional half bridge (HB) submodule or the full bridge (FB) submodules. A clamp double (CD) submodule has been proposed and is basically a series connection of two half bridge submodules with better fault handling capability. But it uses an additional switch and two diodes in normal operation which increases the semiconductor losses.
Multilevel converters that are scalable, have less complexity and/or have lower semiconductor losses are always desired.